The present invention relates to a supercritical wing for aircraft.
A supercritical wing is defined or commonly understood to be an airfoil designed for subsonic flights, but having a flow field along its upper surface which flow field includes an extended portion that is supersonic. Wings and airfoils of this type are usually designed for a Mach number not exceeding 0.85. A wing of this type is, for example, disclosed in German printed patent application 27 12 717 (see also U.S. patent application, Ser. No. 888,319, filed Mar. 20, 1978 now U.S. Pat. No. 4,455,003) The upper surface of this particular wing develops a significant transsonic suction region which drops continuously toward the rear end, substantially without development of compression shocks. The same is not true with regard to earlier wing designs such as shown in U.S. Pat. Nos. 3,952,971 and 4,072,282.
Shock-free behavior of the wing as per U.S. Pat. No. 4,455,003 (Ser. No. 888,319) is true only for a particular angle of attack and a particular Mach number. Upon increasing either, a compression shock will develop, increasing in intensity with increasing angle of attack and/or Mach number. However, that particular wing is designed to stabilize the location of that shock on the wing's upper surface. This way, one avoids changes of the longitudinal moment in the off-design range.
It was observed, however, that this known wing is limited in its range of use by the so-called buffet onset, i.e., by the development of in-stationary, shock-induced separations and the effect such separations have upon the flow pattern around the wing.